Continuing directly from "Meet the New Boss" Castiel's vessel (Misha Collins) cackles at Dean (Jensen Ackles), but the black is rapidly spreading and starting to drip, then flow.

Dean wonders how many leviathans are inside Castiel. Leviathaniel declares their intention to come back for our heroes, then staggers away. Bobby (Jim Beaver) awakens in time to catch the last bit. A black and oozy Leviathaniel has staggered into the 'Tricity' municipal water reservoir and dissolves into it, leaving his trench coat to wash up at Dean's feet.

A little girl, Annie (Olivia Steele-Falconer), and a mechanic, Edgar (Benito Martinez), along with many others drink or are splashed with blackness and possessed by leviathans. They know what their vessels know and begin coordinating immediately.

Inspired by "Dr. Sexy, MD," Annie's plan for feeding insatiable leviathans involves eating a doctor, Gaines (Cameron Bancroft), at Sioux Falls Hospital. Other leviathan are installed into the hospital administrator (Michael Rys) and head nurse (Lori Ann Triolo). Now they can eat patients and cover it up leaving only a statistical anomaly.

Sheriff Jody Mills (Kim Rhodes) from "Dead Men Don't Wear Plaid" is in the hospital recovering from a appendectomy when Dr. Leviathan takes his first victim, her room mate (Patti Allan). She alerts Bobby, who rescues her, scopes out the situation and determines that silver buckshot is an ineffective leviathan deterrent.

With Sam dangerously unreliable, Dean goes solo to check out the swim team incident, and when Bobby goes to rescue Sheriff Mills, Sam is left alone and vulnerable to a vision of Dean returning and taking him out to a leviathan infestation. Real Dean tracks him down and gives him a touchstone to reality. Pain in hell is qualitatively different than real world pain. When Dean abuses Sam's cut hand he is able to banish the visions for a while.

Bobby calls from the car (invest in a hands-free headset, Bobby!) and reports on the leviathan invasion of the hospital. The boys go to Bobby's place to meet him, but it's a burned out shell and there's no Bobby. Dean vows to Bobby's voice mail to take Sam with him as he commits suicide if Bobby is really gone.

They wander the junkyard grounds calling for Bobby until Edgar shows up. Melee ensues, Dean's leg is broken, Sam receives a vicious shovel to the head and Dean releases a car conveniently suspended above the yard on a crane onto Edgar. Crushed beneath the car, Edgar oozes black in a satisfying way as Dean calls 911.

Unfortunately, the ambulance is taking them to Sioux Falls General and back at the junk yard, Edgar reabsorbs his ooze and begins twitching. Fade to black.

Points Of Interest

1. We don't meet the boss leviathan, but for now he speaks through Edgar. He wants leviathan activities to stay out of the media.

2. When half of the swim team ate the other half in Stockville High School, North Kansas, Annie failed in her duties as their supervisor.

3. Phantom Lucifer (Mark Pellegrino) tells Sam he is still in hell, and Bobby and Dean are just visions. Sam shares this with Dean and Bobby, but each side calls the other the actual phantoms; so Sam has no solid point of reference.

4. Sam's visions enable him to competently drive a car a considerable distance while at the same time making him think that he was the passenger that whole time.

5. In the ambulance, Sam sees Lucifer, who admits that he might not be real, but that doesn't mean he's going away. The paramedic (Justin Breault) reports that Sam probably has inter-cranial bleeding just before Sam has a seizure.

What Worked

Another plot-dense hour, this episode sets up the threat of the leviathan and Sam's hell-flooded mind efficiently and effectively. As befits an Edlund script, the dialog was particularly pithy:

--Bobby on Dean's insistence that he is ok: "Weren't you pissed at him when he said the same thing just a couple of hours before he spilled his marbles all over the floor?"

--Jody on observed leviathan activity: "Huh. Not weird at all."

--Bobby's voicemail greeting: "This is Bobby Singer's direct hotline, you should not have this number."

--Edgar to Dean: "Winchester. Congratulations. Apparently you two are competent enough to warrant annihilating. I'd take it as a compliment."

What Didn't Work

Leviathan-possessed Castiel/Jimmy was fun. Too bad he went away so quickly.

Also, disappearing down the "drain" during the teaser was an exit lacking in resonance or the epic punch Castiel deserved.